Analysis of the UV-Ozone-Treated SnO2 Electron Transporting Layer in Planar Perovskite Solar Cells for High Performance and Reduced Hysteresis

Tin oxide (SnO2) is widely used as an electron transporting layer (ETL) in perovskite solar cells (PSCs) because of its good transparency, band alignment to perovskite, and stability. The interface between the ETL and the perovskite in the PSCs affects the charge extraction process and influences the optoelectronic properties. Surface treatment of SnO2, such as the UV-ozone (UVO) treatment, is shown to enhance the efficiency and reduce the light soaking effect of the PSCs. Herein, the success in control and suppressing hysteresis reaching the highest photoconversion efficiency of 19.4% with negligible hysteresis for the growth of the devices on SnO2 treated with UVO for 60 min is reported. The wettability of the treated SnO2 is well matched with the polar solvent of the perovskite solution, leading to complete coverage of the substrate, although the treatment does not affect the morphology and the crystallinity of the perovskite thin films. Impedance spectroscopy measurement analysis clearly indicates the decrease in the recombination rate after the UVO treatment and the reduction in low frequency capacitance causing a reduction in the current-potential curve hysteresis.